(1) Field of the Invention
The present invention relates to an exhaust treatment apparatus for an engine. Specifically, the present invention relates to an exhaust treatment apparatus for an engine that can improve continuance of combustion flame of combustible gas.
(2) Description of Related Art
A conventional exhaust treatment apparatus for an engine includes an oxidation catalyst disposed in an exhaust passage, a combustible gas generator, and a combustible gas supplying passage. The combustible gas supplying passage is disposed in parallel to and beneath the exhaust passage. A heat releasing port is opened in an upstream side in the exhaust passage from the oxidation catalyst and in a downstream side in the combustible gas supplying passage. The exhaust passage and the combustible gas supplying passage communicate with each other through the heat releasing port. An ignition apparatus is disposed beneath the heat releasing port. The heat of flaming combustion of combustible gas ignited by the ignition apparatus is supplied to the exhaust passage to raise the temperature of exhaust in the exhaust passage. A flame holding plate is provided beneath the heat releasing port in a downstream side in the combustible gas supplying passage from the ignition apparatus (e.g., see FIGS. 1A and 2 of JP 2012-188972 A).
The exhaust treatment apparatus of this type is advantageous in that the oxidation catalyst can be activated even when the temperature of exhaust is low, because the temperature of exhaust is raised by the heat of flaming combustion of combustible gas.
However, this conventional technique involves a problem since the ignition apparatus is exposed to the exhaust passage from beneath.
<<Problem>>
Continuance of combustion flame of combustible gas is poor.
Since the ignition apparatus is exposed to the exhaust passage from beneath, exhaust that passes the exhaust passage tends to enter the area surrounding the ignition apparatus from above the ignition apparatus. Accordingly, exhaust tends to blow off combustion flame of combustible gas, and thus continuance of combustion flame of combustible gas is poor.